/*
** $Id: lparser.c,v 2.42.1.3 2007/12/28 15:32:23 roberto Exp $
** Lua Parser
** See Copyright Notice in lua.h
*/


#include <string.h>
#include <stdlib.h>

#define lparser_c
#define LUA_CORE

#include "lua.h"

#include "lcode.h"
#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "llex.h"
#include "lmem.h"
#include "lobject.h"
#include "lopcodes.h"
#include "lparser.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"



#define hasmultret(k)       ((k) == VCALL || (k) == VVARARG)

#define getlocvar(fs, i)    ((fs)->f->locvars[(fs)->actvar[i]])

#define luaY_checklimit(fs,v,l,m)   if ((v)>(l)) errorlimit(fs,l,m)


/*
** nodes for block list (list of active blocks)
*/
typedef struct BlockCnt
{
    struct BlockCnt *previous;  /* chain */
    int breaklist;  /* list of jumps out of this loop */
    lu_byte nactvar;  /* # active locals outside the breakable structure */
    lu_byte upval;  /* true if some variable in the block is an upvalue */
    lu_byte isbreakable;  /* true if `block' is a loop */
} BlockCnt;



/*
** prototypes for recursive non-terminal functions
*/
static void chunk(LexState *ls);
static void expr(LexState *ls, expdesc *v);


static void anchor_token(LexState *ls)
{
    if (ls->t.token == TK_NAME || ls->t.token == TK_STRING)
    {
        TString *ts = ls->t.seminfo.ts;
        luaX_newstring(ls, getstr(ts), ts->tsv.len);
    }
}


static void error_expected(LexState *ls, int token)
{
    luaX_syntaxerror(ls,
                     luaO_pushfstring(ls->L, LUA_QS " expected", luaX_token2str(ls, token)));
}


static void errorlimit(FuncState *fs, int limit, const char *what)
{
    const char *msg = (fs->f->linedefined == 0) ?
                      luaO_pushfstring(fs->L, "main function has more than %d %s", limit, what) :
                      luaO_pushfstring(fs->L, "function at line %d has more than %d %s",
                                       fs->f->linedefined, limit, what);
    luaX_lexerror(fs->ls, msg, 0);
}


static int testnext(LexState *ls, int c)
{
    if (ls->t.token == c)
    {
        luaX_next(ls);
        return 1;
    }
    else return 0;
}


static void check(LexState *ls, int c)
{
    if (ls->t.token != c)
        error_expected(ls, c);
}

static void checknext(LexState *ls, int c)
{
    check(ls, c);
    luaX_next(ls);
}


#define check_condition(ls,c,msg)   { if (!(c)) luaX_syntaxerror(ls, msg); }



static void check_match(LexState *ls, int what, int who, int where)
{
    if (!testnext(ls, what))
    {
        if (where == ls->linenumber)
            error_expected(ls, what);
        else
        {
            luaX_syntaxerror(ls, luaO_pushfstring(ls->L,
                                                  LUA_QS " expected (to close " LUA_QS " at line %d)",
                                                  luaX_token2str(ls, what), luaX_token2str(ls, who), where));
        }
    }
}


static TString *str_checkname(LexState *ls)
{
    TString *ts;
    check(ls, TK_NAME);
    ts = ls->t.seminfo.ts;
    luaX_next(ls);
    return ts;
}


static void init_exp(expdesc *e, expkind k, int i)
{
    e->f = e->t = NO_JUMP;
    e->k = k;
    e->u.s.info = i;
}


static void codestring(LexState *ls, expdesc *e, TString *s)
{
    init_exp(e, VK, luaK_stringK(ls->fs, s));
}


static void checkname(LexState *ls, expdesc *e)
{
    codestring(ls, e, str_checkname(ls));
}


static int registerlocalvar(LexState *ls, TString *varname)
{
    FuncState *fs = ls->fs;
    Proto *f = fs->f;
    int oldsize = f->sizelocvars;
    luaM_growvector(ls->L, f->locvars, fs->nlocvars, f->sizelocvars,
                    LocVar, SHRT_MAX, "too many local variables");
    while (oldsize < f->sizelocvars) f->locvars[oldsize++].varname = NULL;
    f->locvars[fs->nlocvars].varname = varname;
    luaC_objbarrier(ls->L, f, varname);
    return fs->nlocvars++;
}


#define new_localvarliteral(ls,v,n) \
  new_localvar(ls, luaX_newstring(ls, "" v, (sizeof(v)/sizeof(char))-1), n)


static void new_localvar(LexState *ls, TString *name, int n)
{
    FuncState *fs = ls->fs;
    luaY_checklimit(fs, fs->nactvar + n + 1, LUAI_MAXVARS, "local variables");
    fs->actvar[fs->nactvar + n] = cast(unsigned short, registerlocalvar(ls, name));
}


static void adjustlocalvars(LexState *ls, int nvars)
{
    FuncState *fs = ls->fs;
    fs->nactvar = cast_byte(fs->nactvar + nvars);
    for (; nvars; nvars--)
    {
        getlocvar(fs, fs->nactvar - nvars).startpc = fs->pc;
    }
}


static void removevars(LexState *ls, int tolevel)
{
    FuncState *fs = ls->fs;
    while (fs->nactvar > tolevel)
        getlocvar(fs, --fs->nactvar).endpc = fs->pc;
}


static int indexupvalue(FuncState *fs, TString *name, expdesc *v)
{
    int i;
    Proto *f = fs->f;
    int oldsize = f->sizeupvalues;
    for (i = 0; i < f->nups; i++)
    {
        if (fs->upvalues[i].k == v->k && fs->upvalues[i].info == v->u.s.info)
        {
            lua_assert(f->upvalues[i] == name);
            return i;
        }
    }
    /* new one */
    luaY_checklimit(fs, f->nups + 1, LUAI_MAXUPVALUES, "upvalues");
    luaM_growvector(fs->L, f->upvalues, f->nups, f->sizeupvalues,
                    TString *, MAX_INT, "");
    while (oldsize < f->sizeupvalues) f->upvalues[oldsize++] = NULL;
    f->upvalues[f->nups] = name;
    luaC_objbarrier(fs->L, f, name);
    lua_assert(v->k == VLOCAL || v->k == VUPVAL);
    fs->upvalues[f->nups].k = cast_byte(v->k);
    fs->upvalues[f->nups].info = cast_byte(v->u.s.info);
    return f->nups++;
}


static int searchvar(FuncState *fs, TString *n)
{
    int i;
    for (i = fs->nactvar - 1; i >= 0; i--)
    {
        if (n == getlocvar(fs, i).varname)
            return i;
    }
    return -1;  /* not found */
}


static void markupval(FuncState *fs, int level)
{
    BlockCnt *bl = fs->bl;
    while (bl && bl->nactvar > level) bl = bl->previous;
    if (bl) bl->upval = 1;
}


static int singlevaraux(FuncState *fs, TString *n, expdesc *var, int base)
{
    if (fs == NULL)    /* no more levels? */
    {
        init_exp(var, VGLOBAL, NO_REG);  /* default is global variable */
        return VGLOBAL;
    }
    else
    {
        int v = searchvar(fs, n);  /* look up at current level */
        if (v >= 0)
        {
            init_exp(var, VLOCAL, v);
            if (!base)
                markupval(fs, v);  /* local will be used as an upval */
            return VLOCAL;
        }
        else    /* not found at current level; try upper one */
        {
            if (singlevaraux(fs->prev, n, var, 0) == VGLOBAL)
                return VGLOBAL;
            var->u.s.info = indexupvalue(fs, n, var);  /* else was LOCAL or UPVAL */
            var->k = VUPVAL;  /* upvalue in this level */
            return VUPVAL;
        }
    }
}


static void singlevar(LexState *ls, expdesc *var)
{
    TString *varname = str_checkname(ls);
    FuncState *fs = ls->fs;
    if (singlevaraux(fs, varname, var, 1) == VGLOBAL)
        var->u.s.info = luaK_stringK(fs, varname);  /* info points to global name */
}


static void adjust_assign(LexState *ls, int nvars, int nexps, expdesc *e)
{
    FuncState *fs = ls->fs;
    int extra = nvars - nexps;
    if (hasmultret(e->k))
    {
        extra++;  /* includes call itself */
        if (extra < 0) extra = 0;
        luaK_setreturns(fs, e, extra);  /* last exp. provides the difference */
        if (extra > 1) luaK_reserveregs(fs, extra - 1);
    }
    else
    {
        if (e->k != VVOID) luaK_exp2nextreg(fs, e);  /* close last expression */
        if (extra > 0)
        {
            int reg = fs->freereg;
            luaK_reserveregs(fs, extra);
            luaK_nil(fs, reg, extra);
        }
    }
}


static void enterlevel(LexState *ls)
{
    if (++ls->L->nCcalls > LUAI_MAXCCALLS)
        luaX_lexerror(ls, "chunk has too many syntax levels", 0);
}


#define leavelevel(ls)  ((ls)->L->nCcalls--)


static void enterblock(FuncState *fs, BlockCnt *bl, lu_byte isbreakable)
{
    bl->breaklist = NO_JUMP;
    bl->isbreakable = isbreakable;
    bl->nactvar = fs->nactvar;
    bl->upval = 0;
    bl->previous = fs->bl;
    fs->bl = bl;
    lua_assert(fs->freereg == fs->nactvar);
}


static void leaveblock(FuncState *fs)
{
    BlockCnt *bl = fs->bl;
    fs->bl = bl->previous;
    removevars(fs->ls, bl->nactvar);
    if (bl->upval)
        luaK_codeABC(fs, OP_CLOSE, bl->nactvar, 0, 0);
    /* a block either controls scope or breaks (never both) */
    lua_assert(!bl->isbreakable || !bl->upval);
    lua_assert(bl->nactvar == fs->nactvar);
    fs->freereg = fs->nactvar;  /* free registers */
    luaK_patchtohere(fs, bl->breaklist);
}


static void pushclosure(LexState *ls, FuncState *func, expdesc *v)
{
    FuncState *fs = ls->fs;
    Proto *f = fs->f;
    int oldsize = f->sizep;
    int i;
    luaM_growvector(ls->L, f->p, fs->np, f->sizep, Proto *,
                    MAXARG_Bx, "constant table overflow");
    while (oldsize < f->sizep) f->p[oldsize++] = NULL;
    f->p[fs->np++] = func->f;
    luaC_objbarrier(ls->L, f, func->f);
    init_exp(v, VRELOCABLE, luaK_codeABx(fs, OP_CLOSURE, 0, fs->np - 1));
    for (i = 0; i < func->f->nups; i++)
    {
        OpCode o = (func->upvalues[i].k == VLOCAL) ? OP_MOVE : OP_GETUPVAL;
        luaK_codeABC(fs, o, 0, func->upvalues[i].info, 0);
    }
}


static void open_func(LexState *ls, FuncState *fs)
{
    lua_State *L = ls->L;
    Proto *f = luaF_newproto(L);
    fs->f = f;
    fs->prev = ls->fs;  /* linked list of funcstates */
    fs->ls = ls;
    fs->L = L;
    ls->fs = fs;
    fs->pc = 0;
    fs->lasttarget = -1;
    fs->jpc = NO_JUMP;
    fs->freereg = 0;
    fs->nk = 0;
    fs->np = 0;
    fs->nlocvars = 0;
    fs->nactvar = 0;
    fs->bl = NULL;
    f->source = ls->source;
    f->maxstacksize = 2;  /* registers 0/1 are always valid */
    fs->h = luaH_new(L, 0, 0);
    /* anchor table of constants and prototype (to avoid being collected) */
    sethvalue2s(L, L->top, fs->h);
    incr_top(L);
    setptvalue2s(L, L->top, f);
    incr_top(L);
}


static void close_func(LexState *ls)
{
    lua_State *L = ls->L;
    FuncState *fs = ls->fs;
    Proto *f = fs->f;
    removevars(ls, 0);
    luaK_ret(fs, 0, 0);  /* final return */
    luaM_reallocvector(L, f->code, f->sizecode, fs->pc, Instruction);
    f->sizecode = fs->pc;
    luaM_reallocvector(L, f->lineinfo, f->sizelineinfo, fs->pc, int);
    f->sizelineinfo = fs->pc;
    luaM_reallocvector(L, f->k, f->sizek, fs->nk, TValue);
    f->sizek = fs->nk;
    luaM_reallocvector(L, f->p, f->sizep, fs->np, Proto *);
    f->sizep = fs->np;
    luaM_reallocvector(L, f->locvars, f->sizelocvars, fs->nlocvars, LocVar);
    f->sizelocvars = fs->nlocvars;
    luaM_reallocvector(L, f->upvalues, f->sizeupvalues, f->nups, TString *);
    f->sizeupvalues = f->nups;
    lua_assert(luaG_checkcode(f));
    lua_assert(fs->bl == NULL);
    ls->fs = fs->prev;
    /* last token read was anchored in defunct function; must reanchor it */
    if (fs) anchor_token(ls);
    L->top -= 2;  /* remove table and prototype from the stack */
}


Proto *luaY_parser(lua_State *L, ZIO *z, Mbuffer *buff, const char *name)
{
    struct LexState lexstate;
    struct FuncState *pfuncstate = (struct FuncState *)malloc(sizeof(struct FuncState));
    Proto *res;
    TString *tname = luaS_new(L, name);
    setsvalue2s(L, L->top, tname);  /* protect name */
    incr_top(L);
    lexstate.buff = buff;
    luaX_setinput(L, &lexstate, z, tname);
    open_func(&lexstate, pfuncstate);
    pfuncstate->f->is_vararg = VARARG_ISVARARG;  /* main func. is always vararg */
    luaX_next(&lexstate);  /* read first token */
    chunk(&lexstate);
    check(&lexstate, TK_EOS);
    close_func(&lexstate);
    L->top--; /* remove 'name' from stack */
    lua_assert(pfuncstate->prev == NULL);
    lua_assert(pfuncstate->f->nups == 0);
    lua_assert(lexstate.fs == NULL);
    res = pfuncstate->f;
    free(pfuncstate);
    return res;
}



/*============================================================*/
/* GRAMMAR RULES */
/*============================================================*/


static void field(LexState *ls, expdesc *v)
{
    /* field -> ['.' | ':'] NAME */
    FuncState *fs = ls->fs;
    expdesc key;
    luaK_exp2anyreg(fs, v);
    luaX_next(ls);  /* skip the dot or colon */
    checkname(ls, &key);
    luaK_indexed(fs, v, &key);
}


static void yindex(LexState *ls, expdesc *v)
{
    /* index -> '[' expr ']' */
    luaX_next(ls);  /* skip the '[' */
    expr(ls, v);
    luaK_exp2val(ls->fs, v);
    checknext(ls, ']');
}


/*
** {======================================================================
** Rules for Constructors
** =======================================================================
*/


struct ConsControl
{
    expdesc v;  /* last list item read */
    expdesc *t;  /* table descriptor */
    int nh;  /* total number of `record' elements */
    int na;  /* total number of array elements */
    int tostore;  /* number of array elements pending to be stored */
};


static void recfield(LexState *ls, struct ConsControl *cc)
{
    /* recfield -> (NAME | `['exp1`]') = exp1 */
    FuncState *fs = ls->fs;
    int reg = ls->fs->freereg;
    expdesc key, val;
    int rkkey;
    if (ls->t.token == TK_NAME)
    {
        luaY_checklimit(fs, cc->nh, MAX_INT, "items in a constructor");
        checkname(ls, &key);
    }
    else  /* ls->t.token == '[' */
        yindex(ls, &key);
    cc->nh++;
    checknext(ls, '=');
    rkkey = luaK_exp2RK(fs, &key);
    expr(ls, &val);
    luaK_codeABC(fs, OP_SETTABLE, cc->t->u.s.info, rkkey, luaK_exp2RK(fs, &val));
    fs->freereg = reg;  /* free registers */
}


static void closelistfield(FuncState *fs, struct ConsControl *cc)
{
    if (cc->v.k == VVOID) return;  /* there is no list item */
    luaK_exp2nextreg(fs, &cc->v);
    cc->v.k = VVOID;
    if (cc->tostore == LFIELDS_PER_FLUSH)
    {
        luaK_setlist(fs, cc->t->u.s.info, cc->na, cc->tostore);  /* flush */
        cc->tostore = 0;  /* no more items pending */
    }
}


static void lastlistfield(FuncState *fs, struct ConsControl *cc)
{
    if (cc->tostore == 0) return;
    if (hasmultret(cc->v.k))
    {
        luaK_setmultret(fs, &cc->v);
        luaK_setlist(fs, cc->t->u.s.info, cc->na, LUA_MULTRET);
        cc->na--;  /* do not count last expression (unknown number of elements) */
    }
    else
    {
        if (cc->v.k != VVOID)
            luaK_exp2nextreg(fs, &cc->v);
        luaK_setlist(fs, cc->t->u.s.info, cc->na, cc->tostore);
    }
}


static void listfield(LexState *ls, struct ConsControl *cc)
{
    expr(ls, &cc->v);
    luaY_checklimit(ls->fs, cc->na, MAX_INT, "items in a constructor");
    cc->na++;
    cc->tostore++;
}


static void constructor(LexState *ls, expdesc *t)
{
    /* constructor -> ?? */
    FuncState *fs = ls->fs;
    int line = ls->linenumber;
    int pc = luaK_codeABC(fs, OP_NEWTABLE, 0, 0, 0);
    struct ConsControl cc;
    cc.na = cc.nh = cc.tostore = 0;
    cc.t = t;
    init_exp(t, VRELOCABLE, pc);
    init_exp(&cc.v, VVOID, 0);  /* no value (yet) */
    luaK_exp2nextreg(ls->fs, t);  /* fix it at stack top (for gc) */
    checknext(ls, '{');
    do
    {
        lua_assert(cc.v.k == VVOID || cc.tostore > 0);
        if (ls->t.token == '}') break;
        closelistfield(fs, &cc);
        switch (ls->t.token)
        {
        case TK_NAME:    /* may be listfields or recfields */
        {
            luaX_lookahead(ls);
            if (ls->lookahead.token != '=')  /* expression? */
                listfield(ls, &cc);
            else
                recfield(ls, &cc);
            break;
        }
        case '[':    /* constructor_item -> recfield */
        {
            recfield(ls, &cc);
            break;
        }
        default:    /* constructor_part -> listfield */
        {
            listfield(ls, &cc);
            break;
        }
        }
    }
    while (testnext(ls, ',') || testnext(ls, ';'));
    check_match(ls, '}', '{', line);
    lastlistfield(fs, &cc);
    SETARG_B(fs->f->code[pc], luaO_int2fb(cc.na)); /* set initial array size */
    SETARG_C(fs->f->code[pc], luaO_int2fb(cc.nh));  /* set initial table size */
}

/* }====================================================================== */



static void parlist(LexState *ls)
{
    /* parlist -> [ param { `,' param } ] */
    FuncState *fs = ls->fs;
    Proto *f = fs->f;
    int nparams = 0;
    f->is_vararg = 0;
    if (ls->t.token != ')')    /* is `parlist' not empty? */
    {
        do
        {
            switch (ls->t.token)
            {
            case TK_NAME:    /* param -> NAME */
            {
                new_localvar(ls, str_checkname(ls), nparams++);
                break;
            }
            case TK_DOTS:    /* param -> `...' */
            {
                luaX_next(ls);
#if defined(LUA_COMPAT_VARARG)
                /* use `arg' as default name */
                new_localvarliteral(ls, "arg", nparams++);
                f->is_vararg = VARARG_HASARG | VARARG_NEEDSARG;
#endif
                f->is_vararg |= VARARG_ISVARARG;
                break;
            }
            default:
                luaX_syntaxerror(ls, "<name> or " LUA_QL("...") " expected");
            }
        }
        while (!f->is_vararg && testnext(ls, ','));
    }
    adjustlocalvars(ls, nparams);
    f->numparams = cast_byte(fs->nactvar - (f->is_vararg & VARARG_HASARG));
    luaK_reserveregs(fs, fs->nactvar);  /* reserve register for parameters */
}


static void body(LexState *ls, expdesc *e, int needself, int line)
{
    /* body ->  `(' parlist `)' chunk END */
    FuncState *pnew_fs = (FuncState *)malloc(sizeof(FuncState));
    open_func(ls, pnew_fs);
    pnew_fs->f->linedefined = line;
    checknext(ls, '(');
    if (needself)
    {
        new_localvarliteral(ls, "self", 0);
        adjustlocalvars(ls, 1);
    }
    parlist(ls);
    checknext(ls, ')');
    chunk(ls);
    pnew_fs->f->lastlinedefined = ls->linenumber;
    check_match(ls, TK_END, TK_FUNCTION, line);
    close_func(ls);
    pushclosure(ls, pnew_fs, e);
    free(pnew_fs);
}


static int explist1(LexState *ls, expdesc *v)
{
    /* explist1 -> expr { `,' expr } */
    int n = 1;  /* at least one expression */
    expr(ls, v);
    while (testnext(ls, ','))
    {
        luaK_exp2nextreg(ls->fs, v);
        expr(ls, v);
        n++;
    }
    return n;
}


static void funcargs(LexState *ls, expdesc *f)
{
    FuncState *fs = ls->fs;
    expdesc args;
    int base, nparams;
    int line = ls->linenumber;
    switch (ls->t.token)
    {
    case '(':    /* funcargs -> `(' [ explist1 ] `)' */
    {
        if (line != ls->lastline)
            luaX_syntaxerror(ls, "ambiguous syntax (function call x new statement)");
        luaX_next(ls);
        if (ls->t.token == ')')  /* arg list is empty? */
            args.k = VVOID;
        else
        {
            explist1(ls, &args);
            luaK_setmultret(fs, &args);
        }
        check_match(ls, ')', '(', line);
        break;
    }
    case '{':    /* funcargs -> constructor */
    {
        constructor(ls, &args);
        break;
    }
    case TK_STRING:    /* funcargs -> STRING */
    {
        codestring(ls, &args, ls->t.seminfo.ts);
        luaX_next(ls);  /* must use `seminfo' before `next' */
        break;
    }
    default:
    {
        luaX_syntaxerror(ls, "function arguments expected");
        return;
    }
    }
    lua_assert(f->k == VNONRELOC);
    base = f->u.s.info;  /* base register for call */
    if (hasmultret(args.k))
        nparams = LUA_MULTRET;  /* open call */
    else
    {
        if (args.k != VVOID)
            luaK_exp2nextreg(fs, &args);  /* close last argument */
        nparams = fs->freereg - (base + 1);
    }
    init_exp(f, VCALL, luaK_codeABC(fs, OP_CALL, base, nparams + 1, 2));
    luaK_fixline(fs, line);
    fs->freereg = base + 1;  /* call remove function and arguments and leaves
                            (unless changed) one result */
}




/*
** {======================================================================
** Expression parsing
** =======================================================================
*/


static void prefixexp(LexState *ls, expdesc *v)
{
    /* prefixexp -> NAME | '(' expr ')' */
    switch (ls->t.token)
    {
    case '(':
    {
        int line = ls->linenumber;
        luaX_next(ls);
        expr(ls, v);
        check_match(ls, ')', '(', line);
        luaK_dischargevars(ls->fs, v);
        return;
    }
    case TK_NAME:
    {
        singlevar(ls, v);
        return;
    }
    default:
    {
        luaX_syntaxerror(ls, "unexpected symbol");
        return;
    }
    }
}


static void primaryexp(LexState *ls, expdesc *v)
{
    /* primaryexp ->
          prefixexp { `.' NAME | `[' exp `]' | `:' NAME funcargs | funcargs } */
    FuncState *fs = ls->fs;
    prefixexp(ls, v);
    for (;;)
    {
        switch (ls->t.token)
        {
        case '.':    /* field */
        {
            field(ls, v);
            break;
        }
        case '[':    /* `[' exp1 `]' */
        {
            expdesc key;
            luaK_exp2anyreg(fs, v);
            yindex(ls, &key);
            luaK_indexed(fs, v, &key);
            break;
        }
        case ':':    /* `:' NAME funcargs */
        {
            expdesc key;
            luaX_next(ls);
            checkname(ls, &key);
            luaK_self(fs, v, &key);
            funcargs(ls, v);
            break;
        }
        case '(':
        case TK_STRING:
        case '{':    /* funcargs */
        {
            luaK_exp2nextreg(fs, v);
            funcargs(ls, v);
            break;
        }
        default:
            return;
        }
    }
}


static void simpleexp(LexState *ls, expdesc *v)
{
    /* simpleexp -> NUMBER | STRING | NIL | true | false | ... |
                    constructor | FUNCTION body | primaryexp */
    switch (ls->t.token)
    {
    case TK_NUMBER:
    {
        init_exp(v, VKNUM, 0);
        v->u.nval = ls->t.seminfo.r;
        break;
    }
    case TK_STRING:
    {
        codestring(ls, v, ls->t.seminfo.ts);
        break;
    }
    case TK_NIL:
    {
        init_exp(v, VNIL, 0);
        break;
    }
    case TK_TRUE:
    {
        init_exp(v, VTRUE, 0);
        break;
    }
    case TK_FALSE:
    {
        init_exp(v, VFALSE, 0);
        break;
    }
    case TK_DOTS:    /* vararg */
    {
        FuncState *fs = ls->fs;
        check_condition(ls, fs->f->is_vararg,
                        "cannot use " LUA_QL("...") " outside a vararg function");
        fs->f->is_vararg &= ~VARARG_NEEDSARG;  /* don't need 'arg' */
        init_exp(v, VVARARG, luaK_codeABC(fs, OP_VARARG, 0, 1, 0));
        break;
    }
    case '{':    /* constructor */
    {
        constructor(ls, v);
        return;
    }
    case TK_FUNCTION:
    {
        luaX_next(ls);
        body(ls, v, 0, ls->linenumber);
        return;
    }
    default:
    {
        primaryexp(ls, v);
        return;
    }
    }
    luaX_next(ls);
}


static UnOpr getunopr(int op)
{
    switch (op)
    {
    case TK_NOT:
        return OPR_NOT;
    case '-':
        return OPR_MINUS;
    case '#':
        return OPR_LEN;
    default:
        return OPR_NOUNOPR;
    }
}


static BinOpr getbinopr(int op)
{
    switch (op)
    {
    case '+':
        return OPR_ADD;
    case '-':
        return OPR_SUB;
    case '*':
        return OPR_MUL;
    case '/':
        return OPR_DIV;
    case '%':
        return OPR_MOD;
    case '^':
        return OPR_POW;
    case TK_CONCAT:
        return OPR_CONCAT;
    case TK_NE:
        return OPR_NE;
    case TK_EQ:
        return OPR_EQ;
    case '<':
        return OPR_LT;
    case TK_LE:
        return OPR_LE;
    case '>':
        return OPR_GT;
    case TK_GE:
        return OPR_GE;
    case TK_AND:
        return OPR_AND;
    case TK_OR:
        return OPR_OR;
    default:
        return OPR_NOBINOPR;
    }
}


static const struct
{
    lu_byte left;  /* left priority for each binary operator */
    lu_byte right; /* right priority */
} priority[] =    /* ORDER OPR */
{
    {6, 6}, {6, 6}, {7, 7}, {7, 7}, {7, 7},  /* `+' `-' `/' `%' */
    {10, 9}, {5, 4},                 /* power and concat (right associative) */
    {3, 3}, {3, 3},                  /* equality and inequality */
    {3, 3}, {3, 3}, {3, 3}, {3, 3},  /* order */
    {2, 2}, {1, 1}                   /* logical (and/or) */
};

#define UNARY_PRIORITY  8  /* priority for unary operators */


/*
** subexpr -> (simpleexp | unop subexpr) { binop subexpr }
** where `binop' is any binary operator with a priority higher than `limit'
*/
static BinOpr subexpr(LexState *ls, expdesc *v, unsigned int limit)
{
    BinOpr op;
    UnOpr uop;
    enterlevel(ls);
    uop = getunopr(ls->t.token);
    if (uop != OPR_NOUNOPR)
    {
        luaX_next(ls);
        subexpr(ls, v, UNARY_PRIORITY);
        luaK_prefix(ls->fs, uop, v);
    }
    else simpleexp(ls, v);
    /* expand while operators have priorities higher than `limit' */
    op = getbinopr(ls->t.token);
    while (op != OPR_NOBINOPR && priority[op].left > limit)
    {
        expdesc v2;
        BinOpr nextop;
        luaX_next(ls);
        luaK_infix(ls->fs, op, v);
        /* read sub-expression with higher priority */
        nextop = subexpr(ls, &v2, priority[op].right);
        luaK_posfix(ls->fs, op, v, &v2);
        op = nextop;
    }
    leavelevel(ls);
    return op;  /* return first untreated operator */
}


static void expr(LexState *ls, expdesc *v)
{
    subexpr(ls, v, 0);
}

/* }==================================================================== */



/*
** {======================================================================
** Rules for Statements
** =======================================================================
*/


static int block_follow(int token)
{
    switch (token)
    {
    case TK_ELSE:
    case TK_ELSEIF:
    case TK_END:
    case TK_UNTIL:
    case TK_EOS:
        return 1;
    default:
        return 0;
    }
}


static void block(LexState *ls)
{
    /* block -> chunk */
    FuncState *fs = ls->fs;
    BlockCnt *pbl = (BlockCnt *)malloc(sizeof(BlockCnt));
    enterblock(fs, pbl, 0);
    chunk(ls);
    lua_assert(pbl->breaklist == NO_JUMP);
    leaveblock(fs);
    free(pbl);
}


/*
** structure to chain all variables in the left-hand side of an
** assignment
*/
struct LHS_assign
{
    struct LHS_assign *prev;
    expdesc v;  /* variable (global, local, upvalue, or indexed) */
};


/*
** check whether, in an assignment to a local variable, the local variable
** is needed in a previous assignment (to a table). If so, save original
** local value in a safe place and use this safe copy in the previous
** assignment.
*/
static void check_conflict(LexState *ls, struct LHS_assign *lh, expdesc *v)
{
    FuncState *fs = ls->fs;
    int extra = fs->freereg;  /* eventual position to save local variable */
    int conflict = 0;
    for (; lh; lh = lh->prev)
    {
        if (lh->v.k == VINDEXED)
        {
            if (lh->v.u.s.info == v->u.s.info)    /* conflict? */
            {
                conflict = 1;
                lh->v.u.s.info = extra;  /* previous assignment will use safe copy */
            }
            if (lh->v.u.s.aux == v->u.s.info)    /* conflict? */
            {
                conflict = 1;
                lh->v.u.s.aux = extra;  /* previous assignment will use safe copy */
            }
        }
    }
    if (conflict)
    {
        luaK_codeABC(fs, OP_MOVE, fs->freereg, v->u.s.info, 0);  /* make copy */
        luaK_reserveregs(fs, 1);
    }
}


static void assignment(LexState *ls, struct LHS_assign *lh, int nvars)
{
    expdesc e;
    check_condition(ls, VLOCAL <= lh->v.k && lh->v.k <= VINDEXED,
                    "syntax error");
    if (testnext(ls, ','))    /* assignment -> `,' primaryexp assignment */
    {
        struct LHS_assign nv;
        nv.prev = lh;
        primaryexp(ls, &nv.v);
        if (nv.v.k == VLOCAL)
            check_conflict(ls, lh, &nv.v);
        luaY_checklimit(ls->fs, nvars, LUAI_MAXCCALLS - ls->L->nCcalls,
                        "variables in assignment");
        assignment(ls, &nv, nvars + 1);
    }
    else    /* assignment -> `=' explist1 */
    {
        int nexps;
        checknext(ls, '=');
        nexps = explist1(ls, &e);
        if (nexps != nvars)
        {
            adjust_assign(ls, nvars, nexps, &e);
            if (nexps > nvars)
                ls->fs->freereg -= nexps - nvars;  /* remove extra values */
        }
        else
        {
            luaK_setoneret(ls->fs, &e);  /* close last expression */
            luaK_storevar(ls->fs, &lh->v, &e);
            return;  /* avoid default */
        }
    }
    init_exp(&e, VNONRELOC, ls->fs->freereg - 1); /* default assignment */
    luaK_storevar(ls->fs, &lh->v, &e);
}


static int cond(LexState *ls)
{
    /* cond -> exp */
    expdesc v;
    expr(ls, &v);  /* read condition */
    if (v.k == VNIL) v.k = VFALSE;  /* `falses' are all equal here */
    luaK_goiftrue(ls->fs, &v);
    return v.f;
}


static void breakstat(LexState *ls)
{
    FuncState *fs = ls->fs;
    BlockCnt *bl = fs->bl;
    int upval = 0;
    while (bl && !bl->isbreakable)
    {
        upval |= bl->upval;
        bl = bl->previous;
    }
    if (!bl)
        luaX_syntaxerror(ls, "no loop to break");
    if (upval)
        luaK_codeABC(fs, OP_CLOSE, bl->nactvar, 0, 0);
    luaK_concat(fs, &bl->breaklist, luaK_jump(fs));
}


static void whilestat(LexState *ls, int line)
{
    /* whilestat -> WHILE cond DO block END */
    FuncState *fs = ls->fs;
    int whileinit;
    int condexit;
    BlockCnt *pbl = (BlockCnt *)malloc(sizeof(BlockCnt));
    luaX_next(ls);  /* skip WHILE */
    whileinit = luaK_getlabel(fs);
    condexit = cond(ls);
    enterblock(fs, pbl, 1);
    checknext(ls, TK_DO);
    block(ls);
    luaK_patchlist(fs, luaK_jump(fs), whileinit);
    check_match(ls, TK_END, TK_WHILE, line);
    leaveblock(fs);
    luaK_patchtohere(fs, condexit);  /* false conditions finish the loop */
    free(pbl);
}


static void repeatstat(LexState *ls, int line)
{
    /* repeatstat -> REPEAT block UNTIL cond */
    int condexit;
    FuncState *fs = ls->fs;
    int repeat_init = luaK_getlabel(fs);
    BlockCnt *pbl1 = (BlockCnt *)malloc(sizeof(BlockCnt)), *pbl2 = (BlockCnt *)malloc(sizeof(BlockCnt));
    enterblock(fs, pbl1, 1);  /* loop block */
    enterblock(fs, pbl2, 0);  /* scope block */
    luaX_next(ls);  /* skip REPEAT */
    chunk(ls);
    check_match(ls, TK_UNTIL, TK_REPEAT, line);
    condexit = cond(ls);  /* read condition (inside scope block) */
    if (!pbl2->upval)    /* no upvalues? */
    {
        leaveblock(fs);  /* finish scope */
        luaK_patchlist(ls->fs, condexit, repeat_init);  /* close the loop */
    }
    else    /* complete semantics when there are upvalues */
    {
        breakstat(ls);  /* if condition then break */
        luaK_patchtohere(ls->fs, condexit);  /* else... */
        leaveblock(fs);  /* finish scope... */
        luaK_patchlist(ls->fs, luaK_jump(fs), repeat_init);  /* and repeat */
    }
    leaveblock(fs);  /* finish loop */
    free(pbl1);
    free(pbl2);
}


static int exp1(LexState *ls)
{
    expdesc e;
    int k;
    expr(ls, &e);
    k = e.k;
    luaK_exp2nextreg(ls->fs, &e);
    return k;
}


static void forbody(LexState *ls, int base, int line, int nvars, int isnum)
{
    /* forbody -> DO block */
    BlockCnt *pbl = (BlockCnt *)malloc(sizeof(BlockCnt));
    FuncState *fs = ls->fs;
    int prep, endfor;
    adjustlocalvars(ls, 3);  /* control variables */
    checknext(ls, TK_DO);
    prep = isnum ? luaK_codeAsBx(fs, OP_FORPREP, base, NO_JUMP) : luaK_jump(fs);
    enterblock(fs, pbl, 0);  /* scope for declared variables */
    adjustlocalvars(ls, nvars);
    luaK_reserveregs(fs, nvars);
    block(ls);
    leaveblock(fs);  /* end of scope for declared variables */
    luaK_patchtohere(fs, prep);
    endfor = (isnum) ? luaK_codeAsBx(fs, OP_FORLOOP, base, NO_JUMP) :
             luaK_codeABC(fs, OP_TFORLOOP, base, 0, nvars);
    luaK_fixline(fs, line);  /* pretend that `OP_FOR' starts the loop */
    luaK_patchlist(fs, (isnum ? endfor : luaK_jump(fs)), prep + 1);
    free(pbl);
}


static void fornum(LexState *ls, TString *varname, int line)
{
    /* fornum -> NAME = exp1,exp1[,exp1] forbody */
    FuncState *fs = ls->fs;
    int base = fs->freereg;
    new_localvarliteral(ls, "(for index)", 0);
    new_localvarliteral(ls, "(for limit)", 1);
    new_localvarliteral(ls, "(for step)", 2);
    new_localvar(ls, varname, 3);
    checknext(ls, '=');
    exp1(ls);  /* initial value */
    checknext(ls, ',');
    exp1(ls);  /* limit */
    if (testnext(ls, ','))
        exp1(ls);  /* optional step */
    else    /* default step = 1 */
    {
        luaK_codeABx(fs, OP_LOADK, fs->freereg, luaK_numberK(fs, 1));
        luaK_reserveregs(fs, 1);
    }
    forbody(ls, base, line, 1, 1);
}


static void forlist(LexState *ls, TString *indexname)
{
    /* forlist -> NAME {,NAME} IN explist1 forbody */
    FuncState *fs = ls->fs;
    expdesc e;
    int nvars = 0;
    int line;
    int base = fs->freereg;
    /* create control variables */
    new_localvarliteral(ls, "(for generator)", nvars++);
    new_localvarliteral(ls, "(for state)", nvars++);
    new_localvarliteral(ls, "(for control)", nvars++);
    /* create declared variables */
    new_localvar(ls, indexname, nvars++);
    while (testnext(ls, ','))
        new_localvar(ls, str_checkname(ls), nvars++);
    checknext(ls, TK_IN);
    line = ls->linenumber;
    adjust_assign(ls, 3, explist1(ls, &e), &e);
    luaK_checkstack(fs, 3);  /* extra space to call generator */
    forbody(ls, base, line, nvars - 3, 0);
}


static void forstat(LexState *ls, int line)
{
    /* forstat -> FOR (fornum | forlist) END */
    FuncState *fs = ls->fs;
    TString *varname;
    BlockCnt *pbl = (BlockCnt *)malloc(sizeof(BlockCnt));
    enterblock(fs, pbl, 1);  /* scope for loop and control variables */
    luaX_next(ls);  /* skip `for' */
    varname = str_checkname(ls);  /* first variable name */
    switch (ls->t.token)
    {
    case '=':
        fornum(ls, varname, line);
        break;
    case ',':
    case TK_IN:
        forlist(ls, varname);
        break;
    default:
        luaX_syntaxerror(ls, LUA_QL("=") " or " LUA_QL("in") " expected");
    }
    check_match(ls, TK_END, TK_FOR, line);
    leaveblock(fs);  /* loop scope (`break' jumps to this point) */
    free(pbl);
}


static int test_then_block(LexState *ls)
{
    /* test_then_block -> [IF | ELSEIF] cond THEN block */
    int condexit;
    luaX_next(ls);  /* skip IF or ELSEIF */
    condexit = cond(ls);
    checknext(ls, TK_THEN);
    block(ls);  /* `then' part */
    return condexit;
}


static void ifstat(LexState *ls, int line)
{
    /* ifstat -> IF cond THEN block {ELSEIF cond THEN block} [ELSE block] END */
    FuncState *fs = ls->fs;
    int flist;
    int escapelist = NO_JUMP;
    flist = test_then_block(ls);  /* IF cond THEN block */
    while (ls->t.token == TK_ELSEIF)
    {
        luaK_concat(fs, &escapelist, luaK_jump(fs));
        luaK_patchtohere(fs, flist);
        flist = test_then_block(ls);  /* ELSEIF cond THEN block */
    }
    if (ls->t.token == TK_ELSE)
    {
        luaK_concat(fs, &escapelist, luaK_jump(fs));
        luaK_patchtohere(fs, flist);
        luaX_next(ls);  /* skip ELSE (after patch, for correct line info) */
        block(ls);  /* `else' part */
    }
    else
        luaK_concat(fs, &escapelist, flist);
    luaK_patchtohere(fs, escapelist);
    check_match(ls, TK_END, TK_IF, line);
}


static void localfunc(LexState *ls)
{
    expdesc v, b;
    FuncState *fs = ls->fs;
    new_localvar(ls, str_checkname(ls), 0);
    init_exp(&v, VLOCAL, fs->freereg);
    luaK_reserveregs(fs, 1);
    adjustlocalvars(ls, 1);
    body(ls, &b, 0, ls->linenumber);
    luaK_storevar(fs, &v, &b);
    /* debug information will only see the variable after this point! */
    getlocvar(fs, fs->nactvar - 1).startpc = fs->pc;
}


static void localstat(LexState *ls)
{
    /* stat -> LOCAL NAME {`,' NAME} [`=' explist1] */
    int nvars = 0;
    int nexps;
    expdesc e;
    do
    {
        new_localvar(ls, str_checkname(ls), nvars++);
    }
    while (testnext(ls, ','));
    if (testnext(ls, '='))
        nexps = explist1(ls, &e);
    else
    {
        e.k = VVOID;
        nexps = 0;
    }
    adjust_assign(ls, nvars, nexps, &e);
    adjustlocalvars(ls, nvars);
}


static int funcname(LexState *ls, expdesc *v)
{
    /* funcname -> NAME {field} [`:' NAME] */
    int needself = 0;
    singlevar(ls, v);
    while (ls->t.token == '.')
        field(ls, v);
    if (ls->t.token == ':')
    {
        needself = 1;
        field(ls, v);
    }
    return needself;
}


static void funcstat(LexState *ls, int line)
{
    /* funcstat -> FUNCTION funcname body */
    int needself;
    expdesc v, b;
    luaX_next(ls);  /* skip FUNCTION */
    needself = funcname(ls, &v);
    body(ls, &b, needself, line);
    luaK_storevar(ls->fs, &v, &b);
    luaK_fixline(ls->fs, line);  /* definition `happens' in the first line */
}


static void exprstat(LexState *ls)
{
    /* stat -> func | assignment */
    FuncState *fs = ls->fs;
    struct LHS_assign v;
    primaryexp(ls, &v.v);
    if (v.v.k == VCALL)  /* stat -> func */
        SETARG_C(getcode(fs, &v.v), 1);  /* call statement uses no results */
    else    /* stat -> assignment */
    {
        v.prev = NULL;
        assignment(ls, &v, 1);
    }
}


static void retstat(LexState *ls)
{
    /* stat -> RETURN explist */
    FuncState *fs = ls->fs;
    expdesc e;
    int first, nret;  /* registers with returned values */
    luaX_next(ls);  /* skip RETURN */
    if (block_follow(ls->t.token) || ls->t.token == ';')
        first = nret = 0;  /* return no values */
    else
    {
        nret = explist1(ls, &e);  /* optional return values */
        if (hasmultret(e.k))
        {
            luaK_setmultret(fs, &e);
            if (e.k == VCALL && nret == 1)    /* tail call? */
            {
                SET_OPCODE(getcode(fs, &e), OP_TAILCALL);
                lua_assert(GETARG_A(getcode(fs, &e)) == fs->nactvar);
            }
            first = fs->nactvar;
            nret = LUA_MULTRET;  /* return all values */
        }
        else
        {
            if (nret == 1)  /* only one single value? */
                first = luaK_exp2anyreg(fs, &e);
            else
            {
                luaK_exp2nextreg(fs, &e);  /* values must go to the `stack' */
                first = fs->nactvar;  /* return all `active' values */
                lua_assert(nret == fs->freereg - first);
            }
        }
    }
    luaK_ret(fs, first, nret);
}


static int statement(LexState *ls)
{
    int line = ls->linenumber;  /* may be needed for error messages */
    switch (ls->t.token)
    {
    case TK_IF:    /* stat -> ifstat */
    {
        ifstat(ls, line);
        return 0;
    }
    case TK_WHILE:    /* stat -> whilestat */
    {
        whilestat(ls, line);
        return 0;
    }
    case TK_DO:    /* stat -> DO block END */
    {
        luaX_next(ls);  /* skip DO */
        block(ls);
        check_match(ls, TK_END, TK_DO, line);
        return 0;
    }
    case TK_FOR:    /* stat -> forstat */
    {
        forstat(ls, line);
        return 0;
    }
    case TK_REPEAT:    /* stat -> repeatstat */
    {
        repeatstat(ls, line);
        return 0;
    }
    case TK_FUNCTION:
    {
        funcstat(ls, line);  /* stat -> funcstat */
        return 0;
    }
    case TK_LOCAL:    /* stat -> localstat */
    {
        luaX_next(ls);  /* skip LOCAL */
        if (testnext(ls, TK_FUNCTION))  /* local function? */
            localfunc(ls);
        else
            localstat(ls);
        return 0;
    }
    case TK_RETURN:    /* stat -> retstat */
    {
        retstat(ls);
        return 1;  /* must be last statement */
    }
    case TK_BREAK:    /* stat -> breakstat */
    {
        luaX_next(ls);  /* skip BREAK */
        breakstat(ls);
        return 1;  /* must be last statement */
    }
    default:
    {
        exprstat(ls);
        return 0;  /* to avoid warnings */
    }
    }
}


static void chunk(LexState *ls)
{
    /* chunk -> { stat [`;'] } */
    int islast = 0;
    enterlevel(ls);
    while (!islast && !block_follow(ls->t.token))
    {
        islast = statement(ls);
        testnext(ls, ';');
        lua_assert(ls->fs->f->maxstacksize >= ls->fs->freereg &&
                   ls->fs->freereg >= ls->fs->nactvar);
        ls->fs->freereg = ls->fs->nactvar;  /* free registers */
    }
    leavelevel(ls);
}

/* }====================================================================== */
